Constant burning pilot for double burner oven

ABSTRACT

Means for preventing extinguishment of a pilot burner in the oven of a gas burning stove either by envelopment with products of combustion or due to concussion which results when the oven door is slammed shut.

United States Patent Kemp [ 1 Feb. 29, 1972 [54] CONSTANT BURNING PILOT FOR DOUBLE BURNER OVEN [72] Inventor:

[73] Assignee: Caloric Corporation [22] Filed: May 27, 1968 211 App]. No 739,976

Wayne T. Kemp, Kutztown, Pa.

Related US. Application Data {63] Continuation of Ser. No. 477,477, Aug. 5, i965, abandoned.

[52] US. Cl ..l26/39 E [58] FieldofSearch ..l26/l9, 39,21

[56] References Cited UNITED STATES PATENTS 3,320,943 5/1967 Crannell et al. ..l26/39 3,338,231 8/1967 Lamar 126/39 Primary Examiner-Edward G. Favors AttarneyHarold A. Murphy and Joseph D. Pannone [57] ABSTRACT Means for preventing extinguishment of a pilot burner in the oven of a gas burning stove either by envelopment with products of combustion or due to concussion which results when the oven door is slammed shut.

5 Claims, 7 Drawing Figures PAIENIEDFEB 29 I972 SHEET 1 BF 2 WAYNE T KEMP ATTORf/[X CONSTANT BURNING PILOT FOR DOUBLE BURNER OVEN This application is a continuation of application, Ser. No. 477,477, filed Aug. 5, 1965 and now abandoned.

My invention relates to a gas burning cooking stove, and, more particularly, it relates to a stove of the type which has an oven compartment with a pilot-ignited baking and roasting burner in the bottom of the compartment and a pilot-ignited broiling burner in the top of said compartment.

One object of the invention is to produce an improved stove of the type set forth.

In the type of stove referred to, the lower burner produces oxygen-deficient gaseous products of combustion which sooner, or later, extinguish the pilot of the upper broiler burner.

'Modern stoves include safety valves which are maintained open by the heat of the pilot flame and which close automatically and shut off the gas completely when the pilot flame is extinguished. This means that the pilot can not be relit by the householder, and a skilled serviceman must be called in to restore service.

According to this invention, and as will be hereinafter set forth in detail, this defect is overcome by supplying the pilot burner with oxygen-bearing room air which made it possible to sustain an adequate flame even when the oven compartment was filled with carbon monoxide and carbon dioxide, and other noncombustion sustaining gases. In initial experiments, one end of a tube was located near the pilot burner and the other end of the tube passed through the back or sidewall of the oven compartment into the room. The lower burner was lit, the broiler burner was lit, and the oven compartment door was closed. Inspection, after a period of time greater than that needed to fill the oven compartment with flame extinguishing gases showed the pilot burner was still lit and that the flame was hard blue. This solved the oxygen-deficiency problem. But it was soon found out that that if the oven compartment door was opened, or closed rapidly, the pilot burner was extinguished and the ordinary expedients, such as enlarging the diameter of the air tube, shortening it, lengthening it, or changing its position, etc., produced no results.

Further, extensive investigation showed the negative pressure induced by rapid opening of the oven door and the excess positive pressure produced by rapid closing of the oven door were responsible for snuffing out the pilot burner flame.

It is therefore a further object of this invention to produce an improved stove wherein the pilot of the upper broiler burner is supplied with oxygen sufiicient to sustain the flame which would otherwise be extinguished by the products of combustion produced by the lower baking burner, and wherein the upper burner pilot is not extinguished by sudden opening and closing of the oven door.

More specifically, the object of the invention is to produce an improved construction whereby the sudden surge normally produced by rapid opening and closing of the oven door is balanced, or neutralized.

A still further object is to produce improved means for accomplishing the foregoing objects which is simple, inexpensive, and durable.

The full nature of the invention will be understood from the following specification and the accompanying drawings in which:

FIG. 1 is a view, partly in section, and partly in elevation, of a cooking stove embodying the invention.

FIG. 2 is an enlarged view looking in the direction of line 2-2 on FIG. 1.

FIG. 3 is a view looking in the direction of line 3-'-3 on FIG. 1.

FIG. 4 is a view looking in the direction of line 44 on FIG. 1.

FIG. 5 is a view looking in the direction of line 5-5 on FIG. 4.

FIG. 6 is a view looking in the direction of line 6-6 on FIG. 4.

FIG. 7 is a view looking in the direction of line 7-7 on FIG. 4.

Except in the respects pointed out below, the stove illustrated may be conventional and includes an oven compartment defined by rear wall 10, sidewalls l2, and 14, and bottom wall 16. The front of the oven compartment is closed by a door 18 which is hinged along its bottom edge in the usual manner.

Above the top 20 of the stove is the usual burner box 22 which is provided with surface burners 24 which are supplied with gas through control valves 26. Below the bottom of the oven compartment is a false bottom or shield 28 which coacts with-oven bottom wall 16 and with sidewalls l0 and 12 to form a compartment 30 for receiving lower burner 32. Burner 32 is provided with combustion air through various openings 34 as indicated by arrows 36. Openings 34 are calibrated to the size of the oven and to the fuel input and may not be tampered with. Also, since they form no part of this invention they will not be further referred to.

The combustion gases produced by lower, baking burner 32 are discharged into the oven compartment through openings 37 formed in oven bottom wall 16. From the oven compartment the combustion gases are discharged through exhaust openings 40 and flue 42 as shown by arrows 44. In the upper portion of the oven compartment there is suitably mounted a broiler burner 46 which is supplied with fuel and air through a venturi 48 and is ignited by a standby pilot 50. Coacting with pilot 50 is a heater pilot (not shown), which cuts off the gas supply should the standby pilot become extinguished. These elements form no part of the present invention and are therefore not shown or described. It is sufficient to point out that pilot 50 is supplied with gas through tube 51 and that it gets its oxygen from the air in the oven compartment and that, when lower burner 32 is ignited, its oxygen-deficient products of combustion will fill the oven compartment and extinguish pilot 50. This makes it impossible to ignite the upper burner 46 automatically.

To prevent extinguishment of the upper burner pilot 50, means is provided for constantly supplying the pilot flame with an adequate mixture of gas and oxygen-bearing air. The means referred to includes a tube 54 formed of a vertical portion 56 and an upwardly slanted portion 58 which enters mixing chamber 61 of pilot burner 50 to mix with the gas supplied by tube 51. The lower end 60 of tube 54 is flared as shown in FIG. 4 and projects into one end of box 62 which is located below shield 28, at the junction of backwall 10 and sidewall 12. The end of box 62 remote from sidewall 12 is provided with openings 64 for admitting oxygen-bearing room air into the box in the direction of arrows 66. It will be noted that portion 58 of the tube 54 forms an obtuse angle with vertical portion 56 and slopes upwardly towards pilot 50 so as to overcome the eddying which develops when any gaseous medium is moved through a right-angle passage. It will also be noted that tube 54 is purposely placed in the oven compartment where it is subjected to high heat so as to maintain the desired convective cffeet within the tube. The room air delivered to the pilot mixing chamber 61 is sufficient to insure constant operation of pilot 50 even when it is surrounded by products of combustion resulting from sustained operation of lower burner 32.

The invention also includes means for the preventing of extinguishment of the pilot 50 due to suction produced by quick opening of the oven door or due to sudden increase in pressure produced by the slamming shut of the oven door. The means referred to includes a relatively large calibrated opening 70 which is formed in bottom wall 16 of the oven and which registers with a relatively large calibrated opening 72 formed in shield 28 through which the flared end 60 of tube 54 enters box 62 to establish communication between the mixing chamber 61 of pilot 50 and the interior of box 62.

The operation is as follows:

Oxygen-bearing room air flows through tube 54 into mixing chamber 61 of pilot 50 so that a suitable gas-air mixture issues out of the pilot orifice to ignite at the tip of the pilot. When the lower burner is ignited, the heat in the oven compartment increases the convective effect and thereby increases the flow of room air to insure an adequate supply of oxygen to pilot 50, which thus remains lit even when the oven compartment is filled with flame-extinguishing products of combustion.

The drastic and sudden reduction in the pressure inside the oven compartment which is produced by rapid opening of the oven door is compensated by room air entering tube 50 through its lower end 60 and by room air entering chamber 30 through openings 34 and entering the oven compartment through opening 70, as shown by arrows 36 and 71. Some air may also enter through flue 42 as shown by arrow 43. The air entering tube 54 and oven compartment 30 is enough to dampen the suction produced by sudden opening of the door to a point sufficient to prevent the extinguishment of the flame of pilot 50.

The sudden increase in pressure which occurs when the oven door is slammed shut and which also extinguishes the pilot flame, is compensated for by effects which are substantially the reverse of those which compensate for the reduction in pressure which is produced by rapid opening of the oven door. Thus, the slamming shut of the oven door causes air compressed in the oven compartment to pass out partly through flue 42 as per arrow 44 and partly down through openings 70 and 72, as per arrows 74, and because holes 64 are relatively small and remote, some of the gases moving down through opening 72 hits the bottom of box 62 and is reflected upwardly through the flared end 60 of tube 54 as per arrow 76. it will be noted that the gases entering box 62 through openings 70 and 72 are mostly, or wholly, in the nature of oxygen-free products of combustion.

It is essential that holes 64 must be large enough to admit the air needed to sustain pilot 50 during sustained operation of lower burner 32, and that these holes must be small enough to insure that some of the gases forced downwardly through openings 70 and 72 by the slamming shut of the door will enter tube 54 as per arrow 76 instead of wholly escaping out of box 62, which would occur if openings 64 were large enough. Also, the flared end of tube 54 must be so spaced from the bottom of box 62 as to receive a sufficient amount of the reflected gases expelled by the slamming shut of the door. it is also necessary that the size of opening 70 be such as to limit the amount of oxygen-deficient gas which passes downwardly through opening 72 and so that, when diluted with room air, the mixture thus produced will have enough oxygen to sustain the pilot.

In a successfully tested prototype, and successfully operating production stoves, the dimensional ratios of the coacting parts were as follows: tube 54 has an OD of about 0.4375 inch and an ID of about 0.3750 inch; opening 72 is about 0.750 inch wide and about 1.25 inch long with a 0.3750 inch radius at each end; the depth of the box from top to bottom is about 0.8812 inch and the distance between the flared end 60 of tube 54 and the bottom of the box is about 0.4062 inch; the length of the box is about inches; its width is about 1.125 inch, and the diameter of the holes 64 is about 0.125 inch.

Installations constructed according to the ratios above set forth operated successfully under laboratory conditions and under actual field-use conditions in stoves having an oven compartment 25Xl6X20 inches, which had a flue 42 of l.0Xl 1.5 inches, and the pilot of which had a heat output of about -175 B.t.u. per hour 1 claim: 1. An oven compartment having: a bottom wall, a lower main burner below said bottom wall, an upper burner, a pilot burner for said upper burner, a tube for supplying air to said pilot burner, there being an opening in said bottom wall, through which said tube passes, the area of said opening being larger than the cross-sectional area of said tube, and a shield positioned below said lower burner,

there berng an opening in sard shield registering with the opening in said bottom wall and leading to the ambient air and through which the lower end of said tube also passes, the area of said opening in said shield also being larger than the area of said tube.

2. The structure recited in claim 1 and a boxlike structure below said opening in said shield and into which the lower end of said tube projects, said boxlike structure having a calibrated opening in a wall thereof remote from said end of said tube.

3. The structure recited in claim 2 in which the bottom of said tube is spaced from the bottom of said boxlike structure.

4. An open front oven compartment having:

a door for closing said opening front, and having a bottom wall,

a lower burner below said bottom wall,

an upper burner above said bottom wall,

a pilot burner for said upper burner,

said pilot burner being disposed in the flow path of the products of combustion of said lower burner, and

means for supplying said pilot burner with fresh air for preventing extinguishment of said pilot by said products of combustion, said means comprising:

a tube having a lower portion disposed in atmosphere external to said compartment and an upper end at said pilot burner, and

means for preventing extinguishment of said pilot burner due to turbulence of air caused by rapid closing or opening of said door,

said last-mentioned means including a first opening formed in said bottom wall,

a bottom shield below said lower burner,

a second opening in said shield and registering with said first opening, said tube extending through said openings, and

a boxlike structure below said shield and enclosing the lower portion of said tube,

the boxlike structure having a calibrated opening in one end thereof remote from said lower portion of said tube,

the end of said lower portion of said tube being spaced from the bottom of said boxlike structure and communicating with said second opening.

5. The structure recited in claim 4 wherein said lower portion of said tube passes through said first and second openings and wherein the area of each of said openings is larger than the cross-sectional area of said tube. 

1. An oven compartment having: a bottom wall, a lower main burner below said bottom wall, an upper burner, a pilot burner for said upper burner, a tube for supplying air to said pilot burner, there being an opening in said bottom wall, through which said tube passes, the area of said opening being larger than the cross-sectional area of said tube, and a shield positioned below said lower burner, there being an opening in said shield registering with the opening in said bottom wall and leading to the ambient air and through which the lower end of said tube also passes, the area of said opening in said shield also being larger than the area of said tube.
 2. The structure recited in claim 1 and a boxlike structure below said opening in said shield and into which the lower end of said tube projects, said boxlike structure having a calibrated opening in a wall thereof remote from said end of said tube.
 3. The structure recited in claim 2 in which the bottom of said tube is spaced from the bottom of said boxlike structure.
 4. An open front oven compartment having: a door for closing said opening front, and having a bottom wall, a lower burner below said bottom wall, an upper burner above said bottom wall, a pilot burner for said upper burner, said pilot burner being disposed in the flow path of the products of combustion of said lower burner, and means for supplying said pilot burner with fresh air for preventing extinguishment of said pilot by said products of combustion, said means comprising: a tube having a lower portion disposed in atmosphere external to said compartment and an upper end at said pilot burner, and means for preventing extinguishment of said pilot burner due to turbulence of air caused by rapid closing or opening of said door, said last-mentioned means including a first opening formed in said bottom wall, a bottom shield below said lower burner, a second opening in said shield and registering with said first opening, said tube extending through said openings, and a boxlike structure below said shield and enclosing the lower portion of said tube, the boxlike structure having a calibrated opening in one end thereof remote from said lower portion of said tube, the end of said lower portion of said tube being spaced from the bottom of said boxlike structure and communicating with said second opening.
 5. The structure recited in claim 4 wherein said lower portion of said tube passes through said first and second openings and wherein the area of each of said openings is larger than the cross-sectional area of said tube. 